1. Field
The present invention relates to processes for stimulating asexual reproduction of plantlets from tissue of immature and mature plants, particularly a variety known as Simmondsia chinensis, that are commonly referred to as Jojoba plants.
2. Prior Art
Asexual reproduction commonly involves cutting of a plant shoot proximate to a bud, across a limb, or the like, to form apical or lateral explants. Such explants are rooted in a medium that stimulates growth, for eventual transplant of the plantlets into soil. Thereby, an exact reproduction or clone, of the original tissue is produced. Asexual reproduction makes possible a duplication of desired characteristics of the original plant, as either found in nature or as produced from seedlings. Such cloned plant can then be used to produce seeds or for cross-pollination with other plants to further improve the species or the like. With the present process, plants can be uniformly produced that have improved pollen yield, superior growth form, or have a desired frost tolerance, moisture tolerance, salt tolerance, seed clustering or seed oil content. Thereby, desirable plant characteristics can be optimized for either a certain locale or to produce a maximum seed yield. The process of the present invention enables the duplication of Simmondsia chinensis, or Jojoba plants selected to have characteristics of superior seed size and or oil content. Such Jojoba oil is very similar to sperm whale oil, and therefore has important commercial potential as a commodity crop.
Processes for stimulating asexual reproduction of plants from tissue, of course, take into account the particular physical characteristics of that plant or plant family and similarly the process of the present invention has been developed for the Simmondsia chinesis, or Jojoba. However, it should be understood that this process may be suitable for plants having characteristics similar thereto, which characteristics include woody stem tissue, shrub-like morphology, and the like.
Heretofore, and with some similarities to the present process, certain processes have been developed for stimulating asexual reproduction of plants, to include the steps of: preparation of plant tissue by appropriately cutting a plant shoot at a limb joint to form an apical explant or across a limb to form a lateral explant, stimulating growth of that explant on a culture medium and rooting on a shoot multiplication medium. Heretofore, pretreatment of such explants has, however, generally involved only a washing in a sterile water than can be dionized or distilled, and has not, as does the present invention, involved a washing in a solution containing a cytokinin. This pretreatment step of the present invention is then chemically complemented by an inclusion of certain hormones to the culture medium that balance with the chemicals used in the pretreatment step so as to provide improved plant growth and increased plant survival rates, and to allow explants to continue to develop thereon for extended time periods without developing callus tissue.
While both the use of conditioning and shoot multiplication mediums are essentially known in the art for stimulating asexual plant reproduction, none have heretofore included both the pretreatment soak in a cytokinin and complementary hormonal chemical additions to the culture medium of the present invention. A pretreatment soak is, however, shown in a U.S. Pat. by Abo, No. 4,217,730, but expressly excludes using a cytokinin in that soak and so is unlike the present process. Examples of other former processes are shown in U.S. Pat. by Corlett, Jr., et al., No. 3,683,550; by Gudin, et al., U.S. Pat. No. 3,816,960; and Sibi, et al., U.S. Pat. No. 4,003,156; and in a patent by McCormick issued in Great Britain and assigned No. 1,387,821.